Arrest of labor is diagnosed when there is no cervical change for greater than _____ hours with adequate contraction.

• A. 2 hours
• B. 4 hours
• C. 6 hours
• D. 8 hours

Answer: (B)

Arrest of labor refers to a lack of progress in dilation during the active phase despite contractions that are strong enough to produce change. The diagnostic threshold used here is a period of no cervical change for 4 hours when the contractions are adequate. Adequate contractions are those capable of producing dilation, often described clinically or quantified as about 200 Montevideo units in a 10-minute window. If contractions are inadequate, the management would focus on augmenting them and reassessing, but the diagnosis of arrest is made once there has been no progress for 4 hours with adequate contractions. Therefore, 4 hours fits the criterion.